In keeping with its status as king of stylized photos, Instagram will feature 13 filters for video. "What we did to photos we just did to video," said Instagram co-founder Kevin Systrom.

Instagram's video app is available on Apple's App Store and Google's Play. In addition to its signature filters, Instagram will enable 15 second videos, custom cover frames, and image stabilization.

The move by the world's largest social network underscores ongoing rivalry between Facebook and Twitter. Twitter's Vine short form video service, launched in January, has amassed a fast following for its quirky and raw six-second videos.

"Image stabilization is a very appealing thing. It's a big product for instagram that will be popular almost immediately. It may have a negative impact on Vine," said Opus Research analyst Greg Sterling.

Facebook has been unleashing a succession of ongoing defensive moves to capture restless mobile audiences in search of the next big thing.

Take Snapchat, the app that enables self-destructing photos and videos, which became a runaway hit, leading Facebook to unleash a similar service, called Poke. Snapchat ranks No. 9 on Apple's App Store.

Vine users posted more videos on Twitter than did Instagram's photo sharers earlier this month, according to measurement firm Topsy Analytics. Vine is the No. 3 iOS app trailed by Instagram at No. 21.

Under siege from mobile startups, Facebook is also at battle with Google's Google+ social network, matching features, as the companies duke it out for display advertising.

Facebook has made mobile its priority. Yet after a year as a public company its stock remains roughly 40% below its offering price of $38.